I am working on a Polysix that refuses to play a note. and hoping somebody has a good troubleshooting process. The CPU board seems to be working OK, with no evidence of acid damage. A lithium CR2032 battery mod installed. Power supply voltages check out, All the front panel LEDs seem to work properly. Tape enable switch is off. I set the board to manual mode and preset reasonable settings but I cant get the board to make a sound. There is activity on the KLM366B including some signals coming from the 8049-217 key assigner MPU.
It would be very helpful to know if there is a signal that is latched or triggered when a key is pressed. I can see pulses scanning the key matrix and when a key is pressed, some signals returning to the MPU, but what does the MPU do when a key is pressed?
Is there a simple and safe way to manually trigger the VCOs...?
Any and all suggestions or advice gratefully accepted...!